Almost 100 people have died after a tornado in the US, that some are speculating could be the worst storm on record there.

The ferocious tornado flattened entire neighbourhoods in the southern suburb of Moore, Oklahoma with winds of up to 200 mph, rendering thousands of people homeless, leaving buildings on fire and landing a direct blow to a school.

Several children were pulled alive from the wreckage of Plaza Towers Elementary School after the devastating, mile-wide tornado reduced the building to heap of rubble and twisted metal.Pictured above: Plaza Towers elementary school was located in a residential area

The power of the storm was captured during a live TV show - the sound almost drowning out the presenter's voice as he's forced to run for cover:

Pictured above: The US National Weather Service tracked the tornado's movements

Rescue

Rescuers passed the children down a "human chain" to get them to medical personnel for treatment.

Roughly 500 students attend the school. It is unclear whether any had been evacuated before the twister hit, but local media reported some children were taken to a nearby church.

Schoolgirl Isabella Rojas managed to escape: 

Firefighters were at the scene digging through the school's debris to reach any children possibly trapped inside.

A second elementary school, Briarwood, was also hit but did not appear to have sustained casualties. Moore's hospital was also badly damaged.

Emergency crews pledged to work through the night across the city to look for survivors, amid reports that another, smaller, storm was on its way to the town of 55,000 people.

This man describes the moment the tornado tore the roof off his house: 

Oklahoma Police Chief Bill Citty has called for patience: 

Governor Mary Fallin knows relatives face an anxious wait for news: 

Becky Nelson's been helping the rescue effort at a school - she says it's a devastating scene: 

Children among dead

The Oklahoma Medical Examiner's Office confirmed the 91 deaths, and said at least 20 children were among the fatalities.

Officials at two hospitals said they were treating more than 140 patients, including around 70 children. Dozens of people were said to be in a critical condition.

Obama responds

President Barack Obama spoke to Oklahoma Governor Mary Fallin on the phone and promised the state all the help it needs as he declared the devastating tornado a major disaster.

Ms Fallin told a news conference "hearts are broken" for the parents looking for their children.

"This is a very sad day for the state of Oklahoma - a very hard day and very tragic day," she said.

"Our prayers and our thoughts are with all the Oklahoma families that have been hit hard by this terrible storm.

"We are doing every single thing that we can to assist those that are in need right now."

She said communication was hard with power lines and mobile phone towers hit by the storm.

The governor said she had deployed 80 Oklahoma National Guard members to help with the recovery effort and assist search and rescue teams who she said were "looking under every single piece of debris" to find anyone that might be injured or lost.

State of emergency

She had already declared a state of emergency for 16 Oklahoma counties due to the tornado threat on Sunday, and added five more on Monday after the storms hit the state capital.

One mother described how she and her children took refuge in their bath as the tornado tore their house apart.

"My husband told us to get in the bathtub immediately and put on a mattress," she said.

She said she had to hold her daughter's hair to stop her slipping away when the tornado struck.

Another family locked themselves inside their cellar - only to have its door ripped open by the twister.

Ricky Stover said: "We thought we'd die. We saw the latch coming undone and we couldn't reach for it ,,, glass and debris started slamming on us."

War zone

Eric Olsen, a radio journalist, said parts of Moore resembled a war zone. He told Sky News: "The devastation here is absolutely mind-blowing. It looks like a bomb has absolutely levelled it. It looks like something you would see in maybe Afghanistan or Iraq."

The National Weather Service gave the twister a preliminary EF-4 classification - on a five-point scale - with winds up to 200mph.

Weather service meteorologist Kelsey Angle said fewer than 1% of all tornadoes ever reach EF-4 or EF-5 levels.

Several other tornado warnings were also in effect following the devastating twister.

It came just a day after two people were confirmed killed by a tornado nearby.

Residents of Moore had been urged to take shelter as the violent storm moved through the area.

The broad, dark funnel cloud was on the ground for 35 minutes before dissipating.

KFOR-TV's news helicopter showed huge swaths of buildings and homes completely levelled, with nothing but wreckage left. Some homes were taken down to their concrete slabs.

Sky News US Correspondent Dominic Waghorn described the damage, saying "whole neighbourhoods just wiped off the map, homes literally stripped to their foundations".

Aerial footage showed vehicles crumpled and overturned in piles of debris on the motorway, and buildings that had become unrecognisable jumbles of rubble.

Utility workers rushed to shut off electricity and gas to the area to prevent further danger from live power lines or natural gas leaks.

Footage of the storm showed the monster twister slowly moving through the area and the flashes of power lines blowing.

Debris found 100 miles away

In Tulsa - 100 miles away - residents reported the debris from the Moore tornado raining down on their neighbourhoods.

The huge tornado was the most recent in a series of twisters that has ravaged towns in the midwest US in recent days as part of a line of violent storms that have stretched from the Canadian border down into Texas.

This part of the country is known as "tornado alley" and residents are trained in how to take shelter. Most towns and cities are equipped with storm sirens that can warn of a coming tornado half an hour before it hits.

The same suburb was hit hard by a tornado in 1999. That storm had the distinction of producing the highest winds ever recorded near the Earth's surface of up to 302 mph.

Country music star Toby Keith, who grew up in the town, said it would persevere.

"Hometown got hit for the gazillionth time. Rise again Moore Oklahoma," he tweeted.